                a. Field of the Invention        
This invention relates generally to the field of medical instruments used for intra-arterial and intravenous introduction of instruments and more specifically to a connection assembly for creating a fluid seal connection between such medical instruments.                b. Background Art        
There are a number of medical procedures which require the introduction of medical instruments into arteries and veins. In one such procedure, known as the Seldinger procedure, a surgical opening is made in a vein or artery with a needle. A guide wire is then inserted through the lumen of the needle into the vein or artery. The needle is withdrawn, leaving the guide wire in place. A dilator is then inserted over the guide wire inside an associated sheath. The dilator and guidewire are removed once the sheath is in place. At this point, various types of catheters or leads may be inserted into the vessel within the lumen of the sheath using the sheath as a conduit to prevent damage to the vessel wall.
In certain medical procedures, for example, where a pacemaker lead is inserted into a patient, a sheath is normally used to guide the pacemaker lead to the appropriate location. Before the pacemaker lead is permanently secured in place and attached to a pacemaker, the sheath must be removed. Because of the size of its lumen, the sheath cannot simply slip over the exterior end of the pacemaker lead as that end of the lead contains a connector coupling for connection to the pacemaker.
Accordingly, there have been disclosed a number of splittable sheaths for use in the introduction of pacemaker lead. These sheaths can be split in half while still surrounding the pacemaker lead. In this use, once the pacemaker lead is in place, the sheath is longitudinally severed and removed from the pacemaker lead. For example, U.S. Pat. No. 4,983,168 discloses such a layered, peel-away hollow sheath, wherein the sheath wall is comprised of at least two layers, an inside cylindrical layer and an outside layer comprising two semi-cylindrical segments defining opposed axially-directed slits or slots therebetween, which comprise tear lines. U.S. Pat. No. 4,596,559 discloses a tear away sheath for use with a disposable introducer set in conjunction with a catheter. U.S. Pat. No. Re. 31,855 discloses a sheath that has an internal molecular orientation which tears easily in a lengthwise direction and with great difficulty in a crosswise or oblique direction. See also U.S. Pat. No. 4,581,025. Longitudinally scored or perforated sheaths are disclosed in U.S. Pat. Nos. 4,166,469; 4,243,050; 4,345,606; and 4,451,256.
Several problems may be encountered during the use of these splittable sheaths. For example, during the introduction of a pacemaker lead, a significant amount of bleeding may occur at the operation site, depending upon the blood pressure present in the vessel. Once the sheath is in place within a vessel, it provides a passageway for the free flow of blood away from the operation site. Further, because of this flow of blood, clotting may occur if the sheath remains in position for an extended period of time. These clots may cause emboli which may pass to the lung and have a detrimental impact on the patient. The use of sheaths may also provide a passageway for the introduction of air into the vessel. The inadvertent introduction of air into the blood system can cause air emboli in the patient that may have negative effects. Because of such problems, splittable sheaths are often removed from the theater of operation as soon as possible, even if it would be preferable to maintain them in position for a longer period of time. Such hurried procedures can result in errors or medical complications.
One method for restricting the flow of blood out of a sheath while a pacemaker lead is being introduced is for the physician to place his thumb over the exposed end of the sheath or to squeeze or pinch the exposed end of the sheath between his thumb and forefinger. However, neither of these methods for reducing the undesired flow of blood and air through the sheath is desirable, because the opportunity for loss of blood and introduction of air is still present. In addition, the structure of these sheaths still requires the surgeon to hold onto it while it is in place in the vessel, thereby limiting the surgeon's ability to perform other medical procedures at the same time. Moreover, squeezing the exposed end of the sheath can deform or even break the sheath, making lead insertion difficult and increasing the likelihood of damage to the lead as it passes through the sheath. Further, even when holding the end of the sheath or pinching the sheath, the flow of blood out of the sheath is not entirely stopped.
For these reasons, a hemostasis valve is often used in conjunction with a sheath to limit blood flow during the introduction of guide wires, catheters, pacemaker leads and other similar medical devices into the heart. This use of a hemostasis valve may, however, cause some issues. For example, because the exterior end of pacemaker leads is larger than the opening in conventional hemostasis valves, it is not possible for pacemaker leads to pass through these conventional hemostasis valves. In many cases the hemostasis valve is designed for use with a specific size of a catheter. Such hemostasis valves have been disclosed, for example, in U.S. Pat. Nos. 5,092,857 and 4,909,798. Another solution to this problem has been to provide splittable hemostasis valves integrally formed with splittable sheaths for the introduction of pacemaker leads as disclosed, for example, in U.S. Pat. Nos. 5,312,355 and 5,125,904. Similarly, splittable hemostasis valves that are not integral with a sheath, but merely connected thereto, may be used (see, for example, U.S. Pat. No. 6,083,207). A further solution to the problem has been to provide a “universal” hemostasis valve, wherein the valve assembly is designed to accommodate leads and catheters of a wide range of diameters.
A wide variety of circumstances can dictate which type of hemostasis valve is chosen for a particular application or in a particular situation. For example, the physician may want to delay introduction of a hemostasis valve onto a sheath until after the sheath is in position. This would suggest that an integral hemostasis valve and sheath is not desirable. In some circumstances, multiple leads or catheters of various diameters may need to be used. In these instances, particularly sized hemostasis valves would not be preferred. In other circumstances, the hemostasis valve may need to be removed during the operation, or perhaps removed and replaced several different times while the sheath remains in place. Such use might counsel against a splittable hemostasis valve that may be prone to leakage once split. Further, it is sometimes necessary to remove the hemostasis valve from the operating theater at a time when the sheath is still in use.
When the particular choice is made to use a non-splitting hemostasis valve, a further problem may arise that remains unaddressed by prior designs. Once introduced into the body intravascularly, leads are often placed in particular and sensitive positions and the intention is for the lead to remain in place. This is particularly true in the case of pacemaker leads that are imbedded in precise locations in the heart muscle to achieve particular results. The problem suggested occurs when attempting to remove the sheath from the patient's blood vessel and from about the lead. In some instances it may be difficult to initiate the tearing of the splittable sheath to remove it. Some amount of force must be applied both distally and radially with respect to the lumen diameter of the sheath in order to pull the two halves of the sheath apart. The initial force required to cause the sheath to begin separation at the proximal end is generally greater than the continuing force required to split the length of the sheath as it is removed from the patient's blood vessel. Sometimes the hemostasis valve is attached to the sheath with a Luer lock interface. When applying this initial force, the lead may be unintentionally moved and either dislodge from or otherwise become misplaced about the heart muscle.
The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and, but is not to be regarded as subject matter by which the scope of the invention is to be bound.